Abstract
This paper investigates the concept of a concentric counter-rotating vertical axis wind turbine (VAWT), consisting of a two stage vertical H-type turbine with three blades on each stage. The model has an inner and an outer stage, rotating in opposition to each other. Both numerical and experimental tests have been performed in order to validate this new concept. Numerical analysis is based on the use of 2.5-dimensional, unsteady simulations using a DOF type of analysis which allows for the two stages to self-adjust their rotation speed. Sliding mesh conformal interfaces are defined between these subdomains to minimize numerical artifacts such as artificial relations or entropy changes. Fully turbulent URANS were carried out in Ansys Fluent software. One key outcome was the momentum coefficient for each stage at different tip wind speed values. Another, more qualitative, outcome is the analysis of vortex shedding, impingement and overall interaction between the stages at different positions and scenarios. Ultimately, the numerical results have been validated using a scaled experimental device which was analyzed in the wind tunnel at different free stream speeds.
Highlights
Concerns regarding global warming have favored the interest of researchers for innovation and research in the field of renewable energy
While offshore wind farms make use of the larger, but less versatile, axial wind turbines, the vertical axis wind turbine (VAWT) independence of the inflow makes them ideally suited for urban environments where flow patterns can be often unpredictable [1]
In order to determine the nominal point of this counter rotating vertical axis wind H type Darrieus turbine, several simulations were carried out, using a URANS degree of freedom (DOF) method
Summary
Concerns regarding global warming have favored the interest of researchers for innovation and research in the field of renewable energy. In Romania, the proportion of wind power peaked at 20% of national requirements in January of 2017, surpassing nuclear power sources. Both vertical and horizontal axis wind turbines are currently employed, with a heightened interest for VAWTs for urban areas. By placing the secondary stage in series, a significant part of the wind power that would otherwise be inaccessible is converted into motion and to electric power. This way, the proposed VAWT can approach Betz's limit [11]
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